Image-forming MR methods, which utilize the interaction between magnetic field and nuclear spins in order to form two-dimensional or three-dimensional images are widely used nowadays, notably in the field of medical diagnostics, because for the imaging of soft tissue they are superior to other imaging methods in many respects, they do not require ionizing radiation, and they are usually not invasive.
According to the MR method in general, the body of a patient or in general an object to be examined is arranged in a strong, uniform magnetic field BO whose direction at the same time defines an axis, normally the z-axis, of the coordinate system on which the measurement is based.
The magnetic field produces different energy levels for the individual nuclear spins in dependence on the applied magnetic field strength which spins can be excited (spin resonance) by application of an alternating electromagnetic field (RF field) of defined frequency, the so called Larmor frequency or MR frequency. From a macroscopic point of view the distribution of the individual nuclear spins produces an overall magnetization which can be deflected out of the state of equilibrium by application of an electromagnetic pulse of appropriate frequency (RF pulse) while the magnetic field extends perpendicularly to the z-axis, so that the magnetization performs a precessional motion about the z-axis.
Any variation of the magnetization can be detected by means of receiving RF antennas, which are arranged and oriented within an examination volume of the MR device in such a manner that the variation of the magnetization is measured in the direction perpendicularly to the z-axis.
In order to realize spatial resolution in the body, switching magnetic field gradients extending along the three main axes are superposed on the uniform magnetic field, leading to a linear spatial dependency of the spin resonance frequency. The signal picked up in the receiving antennas then contains components of different frequencies which can be associated with different locations in the body.
The signal data obtained via the receiving antennas corresponds to the spatial frequency domain and is called k-space data. The k-space data usually includes multiple lines acquired with different phase encoding. Each line is digitized by collecting a number of samples. A set of samples of k-space data is converted to an MR image, e.g. by means of Fourier transformation.
The above description of performing magnetic resonance imaging provides a brief impression on the plurality of parameters which may be adjusted in order to obtain an MR image of a desired portion of the object to be imaged at a desired quality.
Typically, an MR scan protocol used for adjustment of the conditions to be used when performing a magnetic resonance imaging scan can consist of more than 150 adjustable parameters. With the continuing advances in MR sequence development, it is expected that even more methods become available and need to be parameterized in the user interface used at the MR scanner to provide the relevant MR scan protocol parameters to the scanner.
Moreover, radiologists and technicians frequently need to work on different MR systems, from different vendors and are familiar with the user interface of a presently used MR system only up to a certain degree. As a consequence, in these conditions the optimal choice of scan parameters is a difficult, tedious and often iterative task, even for expert users. As a consequence, many scans need to be repeated until image quality is judged good enough. In other cases, the appropriate choice of scan parameters results in inferior image quality below the requested quality standards. Another consequence is that advanced imaging techniques are not used as often as they could be, because the technician may not be aware of the suitable techniques to solve a particular image quality problem or to address a particular patient imaging need.
U.S. Pat. No. 7,315,755 discloses a system and method for communicating a protocol over a network. More specifically, this document relates to a protocol/medical image registration method that permits centralized management of pairs of protocol and a medical image, wherein numerous user terminals are permitted to share protocols as common resources. Consequently, this method permits to make imaging protocols available, however with the drawback that only ‘prefabricated’ protocols are provided, such that with respect to the individual circumstances with respect to an imaging procedure a user is still required to adapt the scan parameters of the selected MR scan protocol in an individual manner. Consequently, the optimal choice of scan parameters is still difficult even for expert users.
From the foregoing it is readily appreciated that there is a need for an improved method of performing a magnetic resonance imaging scan. Further, there is a need for an improved magnetic resonance imaging scanner and an improved computer program product.